It is not fully understood how spatial and temporal information present in the olfactory system represents the various features of simple odors. Although the olfactory bulb (OB) has been studied with single microelectrode recordings and various imaging modalities, these techniques are limited in their exploration of potentially complex interactions present in a population of OB neurons. Within the context of studying the effects of anesthetic agents on various properties of spiking neurons in the rat olfactory bulb, a microelectrode array be used to make electrophysiologic recordings of both spontaneous and odor-evoked neural activity. By comparing the characteristics of the recordings made in the same animal in the awake and anesthetized state, the role of interneurons and information from higher brain centers in the maintenance of ensembles of neurons in the olfactory bulb will be studied. Microelectrode arrays, chronically implanted and simultaneously recording action potentials from a large number of OB neurons in the rat, offer a unique means of studying the ways ensembles of neurons interact while processing olfactory information.